Polyphosphazene chemistry

Moreover, the molecular structural, synthetic, and property nuances of these polymers illustrate many of the attributes, problems, and peculiarities of other inorganic macromolecular systems. Thus, they provide a "case study" for an understanding of what may lie ahead for other systems now being probed at the exploratory level. In short, an understanding of polyphosphazene chemistry forms the basis for an appreciation of a wide variety of related, inorganic-based macromolecular systems and of the relationship between inorganic polymer chemistry and the related fields of organic polymers, ceramic science, and metals. 

Such hybrid molecules and supramolecular solids offer the promise of systems with the flexibility, strength, toughness, and ease of fabrication of polymers, with the high temperature oxidative stability of ceramics, and the electrical or catalytic properties of metals. Polyphosphazene chemistry provides an illustration of what is possible in one representative hybrid system. 

The historical development of polyphosphazene chemistry is compared in Figure 2 with those of other inorganic polymer systems. Its origins can be traced to the late 1800 s, ( 1) although the first... 

With this synthetic and molecular structural diversity, polyphosphazene chemistry has developed into a field that rivals many areas of organic polymer chemistry with respect to the tailored synthesis of polymers for specific experimental or technological uses. Indeed, hybrid systems are also available in which organic polymers bear phosphazene units as side groups. This is discussed in another Chapter. 

This aspect of polyphosphazene chemistry has recently been reviewed elsewhere (36) and only a brief account will be given here. 

Although polyphosphazene chemistry is nearly 100 years old, the technological potential of this class of polymers is only now being realized. 

The polyphosphazene systems comprise some of the most diverse macromolecules yet discovered. Because of space limitations, many aspects of polyphosphazene chemistry... 

Recent developments in the polyphosphazene chemistry have been re-viewed. The role of polyphosphazenes as biodegradable polymers as hydrogels for tissue engineering and as induced helical polymers has been discussed. Preparation and application of poly(thionyl phosphazenes) are discussed in two review chapters. ... 

An understanding of the thermodynamics of ring-chain equilibration reactions is important in Inorganic Chemistry where such reactions abound (sse, for example. Allcock (65), Gee (66), Gimblett (67), and Moedritzer (65)). Two such reactions are found (i) in polyphosphazene chemistry (69) where a polymerisation-depolymerisation equilibrium can be established (70) and (ii) in silicon-sulphur chemistry, where the analogue of the poly(dimethylsiloxane) system has been studied (71) and shown to contain cyclics such as the dimer ( (013)2 SiS)2 the trimer ((CH3)2SiS)3, as well as small amounts of chain molecules of limited chain length. 

In order to prepare hydrolytically stable polythionyiphosphazenes the perchlo-rinated polymers were reacted with nucleophiles to substitute the hydrolytically sensitive main group-element halogen bonds [2]. This type of post-polymerization structural modification is well-established in polyphosphazene chemistry [2,8]. Thus, aryloxide nucleophiles or primary amines were used to substitute the polymers leading to poly(aryloxythionylphosphazenes) 24 and poly(amino-thionylphosphazenes) 25 respectively [35,37] ... 

Perhaps the most widely studied of the dehydrochlorination syntheses are the reactions of halophosphoranes with ammonia to form cyclophosphazenes. This is the classic route from which nearly all cyclo- and polyphosphazene chemistry is derived. Both halogeno- and organocyclophosphazenes have been prepared by this method ... 

Tada, Y., Sato, M., Takeno, N., Nakacho, Y, Shigehara, K., Attempts at lithium single-ionic conduction by anchoring sulfonate anions as terminating groups of oligo(oxyethylene) side chains in comb-type polyphosphazenes. Chemistry of Materials, 1994, 6, 27-30. 

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